noun
straw ashes
Ashes produced by burning straw, traditionally used for various purposes such as fertilizer or in crafts.
昔は藁灰を田んぼの肥料に使った。
In the past, straw ashes were used as fertilizer for rice paddies.
Compound of 藁 (wara, 'straw') and 灰 (hai, 'ashes'). The reading わらばい is a regular rendaku form.